Growling is good!! It is an early warning sign and if you scold a dog for growling it will go straight to biting -- not what you want. Consider why he is growling -- some dogs do so in play (one of mine does!) but if he is *warning* it needs to be recognised as such and you need to address that issue. What is he growling for? Why? Yu suggest he is guarding resources -- eg toys. The growl is a warning not to take the item away. You need to take the time -- and it will take time -- to make taking a toy away an unthreatening behaviour. As I noted above, just grabbing an item away only reinforces all his current concern that he needs to guard the item (all this is explained in the DUnbar book -- did you get a chance to download it and read it?). It also unfortunately isn't a matter of giving a command and hoping it works --- these are all matters of adequately teaching and then reinforcing the training every day, not only at the occasional time you want the dog to respond, when he is likely to just go 'huh?'. It is very much the same with teaching kids --
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Please have a careful read through Ian Dunbar's book as I know it will answer your questions and give you the right training guidance -- you will see he advises several daily sessions where you have fun training and reinforcing the behavour you want. Teaching a dog to 'leave it' and 'drop it', neither of which are things a dog naturally wishes to do, takes focus, encouragement, reward, daily practice, and never ever punishing or scolding the dog for not doing what you are trying to encourage as a positive response. A 10 month old dog is still just a puppy, and if he didn't learn to trade desirable objects for something else from early puppyhood onwards, then it is a far bigger challenge to do now. A willingness to trade and surrender something is a different though a related part of teaching a dog to drop it or leave it. He needs first to be happy to ALWAYS hand over an item -- and THEN you can also ground him in leave it and drop it.
So have a read of Dunbar and follow closely his advice and I am sure you will see an improvement over time. But 'time' is the key word -- this won;t happen in a day or two. It will take a few weeks, maybe even a couple of months, to get real results.
And also get the shoes off the floor and get kids to put them away!!
It is quite risky to have a child try to take something away from a dog -- to get defensive is normal behaviour *if he has not learned otherwise through positive reinforcement*. This is not aggression, it is absolutely normal dog behaviour (think of a toddler with a toy -- it is the same mindset). Please be very careful with children round a dog of any age, and definitely don;t allow the child to try and take something like this off a dog.
The right approach would be to have something the dog loves -- a piece of cheese or meat -- and for an adult to offer that as a swap for the item.
But again: management is 90% of great dog behaviour. If shoes are accessible to the dog, then the dog is going to grab them. Close doors, limit the dog's access to rooms, keep shoes in closets. Consider anything left lying around as fair game as a chew toy. Good management will avoid a lot of frustration.
(there are a couple of essential reading articles on this pinned at the top of the Training forum).